Method for synchronously moving at least two actuator elements, and pneumatic system

Abstract

The invention relates to a method for synchronously moving at least two actuator elements (5) of a pneumatic system (1) for industrial automation, which comprises at least two pneumatic actuators (4) and a valve device (3) for pneumatically actuating the pneumatic actuators (4), wherein each pneumatic actuator (4) has a respective actuator element (5), comprising the steps of: - pneumatically actuating the pneumatic actuators (4) such that each actuator member (5) is displaced into a respective end position; - for each of the pneumatic actuators (4), detecting a respective end pressure value with which the respective pneumatic actuator (4) is actuated when the respective actuator member (5) reaches the end position; - on the basis of the respective end pressure value, generating a respective target pressure curve for each pneumatic actuator (4); - pneumatically actuating each pneumatic actuator (4) according to the respective target pressure curve in order to synchronously move the actuator members (5) to a target position.

Description

[0001] Festo SE & Co. KG, Ruiter Straße 82, 73734 Esslingen

[0002] Method for synchronously moving at least two actuator elements and pneumatic system

[0003] The invention relates to a method for the synchronous movement of at least two actuator elements of a pneumatic system for industrial automation, comprising at least two pneumatic actuators and a valve device for pneumatic actuation of the pneumatic actuators, wherein each pneumatic actuator has a respective actuator element.

[0004] Conventionally, synchronous movement of the actuator elements can be achieved by performing position control for each actuator element.

[0005] From US8840754B2 a device for electrostatic clamping and unclamping of a wafer is known.

[0006] One task of the invention is to provide, in an efficient manner, a method for the synchronous movement of at least two, in particular all, actuator elements. The problem is solved by a method according to claim 1, comprising the steps: pneumatically actuating the pneumatic actuators so that each actuator element is moved into a respective end position for each of the pneumatic actuators, detecting a respective pressure end value with which the respective pneumatic actuator is actuated when the respective actuator element reaches the end position, based on the respective pressure end value, generating a respective target pressure profile for each pneumatic actuator, and pneumatically actuating each pneumatic actuator according to the respective target pressure profile in order to move the actuator elements synchronously to a target position.

[0007] By generating the target pressure profiles based on the previously determined final pressure values, synchronous movement of the actuator elements can be achieved using the target pressure profiles, especially when the pneumatic actuators differ from each other in certain properties relevant to the positioning of the actuator elements, for example in the spring force of a respective spring acting on the actuator element and / or the friction acting on the respective actuator element.

[0008] For example, if a higher final pressure value is detected for a first pneumatic actuator than for a second pneumatic actuator, the valve device can set one or more (or all) of the target pressure values ​​of the target pressure curve for the first pneumatic actuator higher than one or more (or all) of the target pressure values ​​of the target pressure curve for the second pneumatic actuator. The pneumatic actuators can then be conveniently actuated synchronously according to the target pressure curves to ensure synchronous movement of the actuator elements to the target position. Increased friction and / or increased spring force acting on the actuator element of the first pneumatic actuator can be compensated for by the one or more increased target pressure values, thus preventing the actuator element of the first pneumatic actuator from moving more slowly than the actuator element of the second pneumatic actuator.Disturbing influences (such as increased spring force or increased friction) can therefore be taken into account (and in particular compensated for) by generating individual target pressure profiles. Preferably, no position control of the actuator elements is required, so that synchronous movement can be achieved efficiently.

[0009] Advantageous further training is the subject of the subclaims.

[0010] The invention further relates to a pneumatic system for industrial automation, comprising at least two pneumatic actuators and a valve device for pneumatically actuating the pneumatic actuators, wherein each pneumatic actuator has a respective actuator element, wherein the pneumatic system is configured to pneumatically actuate the pneumatic actuators so that each actuator element is moved into a respective end position, to detect a respective end pressure value for each of the pneumatic actuators, with which the respective pneumatic actuator is actuated when the respective actuator element reaches the end position, to generate a respective target pressure profile for each pneumatic actuator based on the target pressure profiles, and to actuate the pneumatic actuators according to the target pressure profiles in order to To move actuator elements synchronously to a target position.

[0011] Further exemplary details and exemplary forms of execution are explained below with reference to the figures. This shows

[0012] Figure 1 is a schematic representation of a pneumatic system, Figure 2 is a block diagram of the pneumatic system with an end-position detection device.

[0013] Figure 3 shows a block diagram of a pneumatic system without an end-position detection device.

[0014] Figure 4 is a diagram of a positional pressure mapping,

[0015] Figure 5 shows diagrams of a target position curve and three target pressure curves, which are calculated based on the target position curve.

[0016] Figure 6 shows a diagram with a position curve, pressure curve and a control signal curve.

[0017] Figure 1 shows an exemplary embodiment of a pneumatic system 1 for industrial automation. The pneumatic system 1 is used, for example, for handling a wafer 2. The pneumatic system 1 is implemented, for instance, as a so-called pinlifting system. The pneumatic system 1 is used, for example, in a semiconductor plant.

[0018] The pneumatic system 1 comprises a valve device 3 and at least two pneumatic actuators 4. The valve device 3 serves to pneumatically actuate the pneumatic actuators 4. By way of example, the pneumatic system 1 comprises three, in particular exactly three, pneumatic actuators 4: a first pneumatic actuator 4a, a second pneumatic actuator 4b, and a third pneumatic actuator 4c. The pneumatic actuators 4 are, by way of example, designed as pneumatic drive cylinders. Preferably, each pneumatic actuator 4 is not designed as a valve. Each pneumatic actuator 4 has a respective actuator element 5, which is, by way of example, designed as a piston assembly. Each piston assembly has a respective piston and, by way of example, a respective piston rod.Each pneumatic actuator 4 has its own pressure chamber 6, which can be selectively pressurized or vented via the valve device 3 to set the respective actuator element 5 in motion. For example, each pneumatic actuator 4 is designed as a single-acting actuator. In particular, each pneumatic actuator 4 has only one pressure chamber 6 and / or one spring 7 acting on the respective actuator element 5.

[0019] For example, each pneumatic actuator 4 has a respective actuator housing 38 in which the respective actuator element 5 and / or the respective pressure chamber 6 is expediently arranged.

[0020] The pneumatic actuators 4 are preferably of identical construction to each other.

[0021] The pneumatic system 1 optionally includes an end-position detection device 8, in particular limit switches. For example, the pneumatic system 1 has a separate end-position detection device 8 for each pneumatic actuator 4, which is, for instance, part of the respective pneumatic actuator 4. Each end-position detection device 8 serves to detect when the respective actuator 4 reaches its end position. For example, each end-position detection device 8 can detect when the respective actuator 5 has reached two different end positions. The respective actuator 5 can be moved, in particular, to a first end position, in which the actuator 5 is, for example, in its fully retracted position, and / or to a second end position, in which the actuator 5 is in its fully extended position.The term "end position" refers specifically to a position in which the actuator 5 can no longer be moved, particularly in the direction in which it was moved to reach the end position. For example, in each end position, the actuator 5 rests against a respective end stop. However, the term "end position" can also refer to any position along the possible path of movement of the respective actuator 5. For example, the end position is determined by positioning the end position detection device 8, in particular the limit switch, along the possible path of movement of the respective actuator 5; that is, the end position is then specifically the position that is detected by the end position detection device 8 (as the end position).

[0022] Preferably, each end-position detection device 8 is not capable of detecting one or more positions, in particular all positions, of the respective actuator 5 between the two end positions. Advantageously, the pneumatic system 1 for the actuator 5 does not include a displacement measuring system and / or a displacement sensor.

[0023] The valve device 3 comprises, by way of example, at least two pressure regulator units 9, each pressure regulator unit 9 being expediently assigned to a respective pneumatic actuator 4 and serving to selectively pressurize or vent the pressure chamber 6 of the respective assigned pneumatic actuator 4. By way of example, each pressure regulator unit 9 is designed as a separate module, in particular as a plate-shaped module. By way of example, the pressure regulator units 9 are arranged in a series arrangement. For example, the pressure regulator units 9 form a valve manifold or are part of a valve manifold. Expediently, each pressure regulator unit 9 is connected to a compressed air source (not shown).

[0024] Each pressure regulator unit 9 is designed to provide a respective output pressure with which the pressure chamber 6 of the respective associated pneumatic actuator 5 is actuated.

[0025] For example, each pressure regulator unit 9 has a valve unit 12 through which the pneumatic actuation of the respective associated pneumatic actuator 4 is effected. For example, each valve unit 12 is designed as a piezoelectric valve unit. Preferably, each valve unit is designed as a proportional valve unit.

[0026] For example, each pressure regulator unit 9 has a respective control unit 13 for controlling the respective valve unit 12, in particular with a control signal 34. Each control unit 13 is, for example, implemented as a microcontroller.

[0027] Each pressure regulator unit 9 is pneumatically connected to a respective pneumatic actuator 4 via a pneumatic line 10 of the pneumatic system 1. The pneumatic lines 10 are, for example, hoses.

[0028] For example, pneumatic system 1 has several

[0029] Pressure sensors 14. Each has an example

[0030] Pressure regulator unit 9 via a respective pressure sensor 14. The pressure sensors 14 serve in particular to detect the respective output pressure - i.e. in particular the pressure of the compressed air in the respective associated pneumatic line 10 and / or the respective associated pressure chamber 6 - and in particular to provide it as an actual pressure value 29.

[0031] Advantageously, each control unit 13 performs a comparison of a current setpoint pressure value of one of the setpoint pressure curves supplied to the respective pressure regulator unit 9 with the respective actual pressure value 29 and, based on the comparison, controls the respective valve unit 12 with the respective control signal 34 in order to cause the output pressure to change towards the setpoint pressure value.

[0032] For example, each pressure regulator unit 9 has a respective (in particular plate-shaped) pressure regulator unit housing 15 in which the respective valve unit 12, the respective control unit 13 and / or the respective pressure sensor 14 is preferably arranged.

[0033] The pressure regulator units 9 are preferably of identical construction to each other.

[0034] By way of example, the valve device 3 further comprises a control unit 11, which is designed in particular as a higher-level control unit, for example as a PLC (programmable logic controller). The control unit 11 is expediently connected to the pressure regulator units 9 via one or more communication lines 16 and expediently transmits setpoint pressure profiles to the pressure regulator units 9 via these communication lines 16.

[0035] For example, pneumatic system 1 has a

[0036] Wafer support 17 for placing the wafer 2. The wafer support 17 has, for example, a wafer support surface 18, which is expediently oriented vertically upwards with its normal vector. The wafer support 17 is, for example, part of a holding device for the wafer 2. The holding device can also be called a chuck and / or is expediently part of the pneumatic system 1. The wafer support 17 is, for example, designed as a round plate.

[0037] The pneumatic system 1 includes, by way of example, a positioning arrangement 19 which is movable relative to the wafer support 17 by means of pneumatic actuators 4 and which serves to position the wafer 2 relative to the wafer support 17. In particular, the positioning arrangement 19 serves to lift the wafer 2 from the wafer support 17 and / or to lower it onto the wafer support 17. Specifically, the wafer 2 is lifted vertically upwards from the wafer support 17 by means of the positioning arrangement 19, as indicated by the arrow 22. The positioning arrangement 19 includes several contact points 21 for the support of the wafer 2. By way of example, the positioning arrangement 19 includes exactly three contact points 21 for the support of the wafer 2. Advantageously, the three contact points 21 are located at the same height and / or are arranged within a horizontal plane distributed relative to each other.Preferably, when lifting or lowering the wafer 2 by means of the positioning arrangement 19, it rests exclusively on the contact points 21.

[0038] Each contact point 21 is assigned to a respective pneumatic actuator 4. In particular, each contact point 21 is set in motion by a respective pneumatic actuator 4. For example, each contact point 21 is part of a respective actuator element 5, in particular a respective piston rod. For example, each contact point 21 is formed by an end of a respective piston rod. Furthermore, each contact point 21 can be part of a respective contact section 20, wherein each contact section 20 is coupled to a respective actuator element 5, in particular attached to it. For example, each contact section 20 is attached to a respective piston rod. The contact sections 20 are part of the positioning arrangement 19.

[0039] The following section will discuss in more detail how synchronous movement of the actuator elements 5 into a target position can be achieved.

[0040] In the illustrated embodiment, such synchronous movement of the actuator elements 5 (and thereby of the contact points 21) can be advantageous in order to avoid the wafer 2 assuming a tilted position during positioning, in particular during lifting and / or lowering.

[0041] Preferably, the pneumatic system 1, in particular the valve device 3, is configured to pneumatically actuate the pneumatic actuators 4, such that each actuator element 5 is moved into a respective end position. Pneumatic actuation is achieved, for example, by venting (or depressurizing) the respective pressure chamber 6, in particular by means of the respective associated pressure regulator unit 9.

[0042] The end position is, for example, the respective maximum extended position of the respective actuator element 5. In particular, the end position is a position at which the respective contact point 21 (in the vertical direction) has reached its maximum height (which can be achieved by the movement of the respective actuator element 5).

[0043] Furthermore, the end position can be the respective maximum retracted position of the respective actuator element 5. In particular, the end position is a position at which the respective contact point 21 (in the vertical direction) has reached its minimum height (which can be achieved by the movement of the respective actuator element 5).

[0044] Preferably, the pneumatic system 1, in particular the valve device 3, is configured to detect a respective end-pressure value for each of the pneumatic actuators 4, with which the respective pneumatic actuator 4 is actuated when the respective actuator element 5 reaches its end position. The respective end-pressure value describes, in particular, the outlet pressure and / or the air pressure in the respective pressure chamber 6 and / or the air pressure of the respective associated pneumatic line 10, which is required to move the respective actuator element 5 into its end position. Advantageously, each end-pressure value is detected by means of the respective associated pressure sensor 14, in particular by the respective associated pressure regulator unit 9.

[0045] The pneumatic actuation of the pneumatic actuators 4, the movement of the actuator elements 5 into the end position, and the acquisition of the final pressure values ​​can collectively be referred to as a learning run or performed within the framework of a learning run. For example, during the learning run, a wafer, a wafer dummy, or another object is located on the contact points 21. Furthermore, it is possible to perform the learning run without an object resting on the contact points 21. The pneumatic system 1, in particular the valve device 3, for example the control unit 11, is configured to generate, and in particular calculate, a respective target pressure profile for each pneumatic actuator 4 based on the respective final pressure value. Each target pressure profile expediently comprises a plurality of target pressure values, in particular the same number of target pressure values. Each target pressure profile is exemplified as a target pressure ramp.In particular, every target pressure curve is monotonic, especially strictly monotonic, increasing or monotonic, especially strictly monotonic, decreasing.

[0046] The pneumatic system 1, in particular the valve device 3, is designed to actuate the pneumatic actuators 4 according to the target pressure profiles in order to move the actuator elements 5 synchronously to a target position. The target position is preferably the end position or a position different from the end position. Advantageously, the contact points 21 are located at the same height in the target position (in particular the end position).

[0047] The pneumatic actuation is achieved, for example, by the control unit 11 successively outputting the respective setpoint pressure values ​​to each pressure regulator unit 9, according to which the respective pressure regulator unit 9 performs the respective pressure regulation in order to regulate the respective output pressure to the respective setpoint pressure value. The setpoint pressure values ​​output to each pressure regulator unit 9 together form a respective setpoint pressure curve.

[0048] Preferably, the target pressure curves differ from each other, particularly in one or more target pressure parameters.

[0049] Values. Advantageously, the controller 11 transmits the target pressure profiles synchronously to the pressure regulator units 9, in particular such that the respective current target pressure value is transmitted to the respective pressure regulator unit 9 at the same time. For example, the controller 11 first transmits a respective first target pressure value to each pressure regulator unit 9 simultaneously, then a respective second target pressure value simultaneously, and then each subsequent respective target pressure value simultaneously, until the respective last target pressure value is transmitted to each pressure regulator unit 9 simultaneously.

[0050] Pneumatic actuation based on the target pressure profiles is expediently carried out during normal operation, especially when the wafer 2 rests on the contact points 21.

[0051] For example, the learning run is performed first, and then the system switches to normal operation, and in normal operation a plurality of pneumatic actuations of the pneumatic actuators 4 are performed successively, using the target pressure profiles generated on the basis of the final pressure values ​​in each case.

[0052] Since the target pressure profiles (formed by the target pressure values) are generated on the basis of the previously determined final pressure values, synchronous movement of the actuator elements 5 (and in particular the contact points 21) can be achieved with the target pressure profiles, even if the pneumatic actuators 4 differ from each other in certain properties relevant for the positioning of the actuator elements 5, for example in the spring force of the respective spring or friction acting on the respective actuator element 5. For example, in the case where a higher final pressure value is detected for the first pneumatic actuator 4a than for the second pneumatic actuator 4b, the valve device 3 can set one or more (or all) setpoint pressure values ​​of the setpoint pressure curve for the first pneumatic actuator 4a higher than one or more (or all) setpoint pressure values ​​of the setpoint pressure curve for the second pneumatic actuator 4b.The higher final pressure value results, for example, from a higher spring force of spring 7 or higher friction acting on actuator 5. This higher spring force and / or higher friction can be compensated for by increasing the target pressure values ​​of the target pressure curve.

[0053] Preferably, the actuator elements 5 (during the actuation of the pneumatic actuators 4 with the generated target pressure profiles) are moved synchronously to the target position over their entire range of motion. Advantageously, the valve device 3 generates the target pressure profiles such that, over the entire range of motion – for example, from the first end position to the second end position or from the second end position to the first end position – all actuator elements 5 always maintain the same position relative to each other along the range of motion (for example, in the vertical direction).

[0054] For example, the valve device 3 actuates the pneumatic actuators 4 according to the target pressure profiles in order to move the contact points 21 synchronously in one direction of movement – ​​for example, vertically upwards or vertically downwards – for positioning the wafer 2, in particular such that the contact points 21 always have the same position relative to each other along the direction of movement – ​​for example, always at the same height relative to each other – during the positioning of the wafer 2. In this way, tilting of the wafer 2 can be prevented.

[0055] Preferably, the pneumatic system 1 does not perform any position control of the actuators 5 during their movement towards the target position. For example, the pneumatic system 1 does not have any position sensors to detect the position of the actuators 5 as they move towards the target position. Optionally, the pneumatic system 1 does not include any position sensor at all to detect the position of an actuator 5.

[0056] According to a preferred embodiment, the valve device 3, in particular the control unit 11, is configured to detect a respective initial pressure value for each of the pneumatic actuators 4 (for example, by means of the pressure sensors 14). The initial pressure value describes the pressure (in particular, the output pressure) with which the respective pneumatic actuator 4 is actuated by the valve device 3 when the respective actuator element 5 begins to move. The initial pressure value can also be referred to as the breakaway pressure. The initial pressure value is, in particular, the pressure required to cause the actuator element 5 to begin moving, especially from an end position. The initial pressure value is detected, in particular, during the learning cycle discussed above.

[0057] Preferably, the valve device 3, in particular the control unit 11, is configured to generate the respective target pressure profile for each pneumatic actuator 4 based on the respective final pressure value and the respective initial pressure value. For example, the valve device 3 uses the initial pressure value as the first target pressure value of the target pressure profile and / or the final pressure value as the last target pressure value of the target pressure profile and / or performs a calculation, for example an interpolation calculation and / or a curve fitting calculation, to determine all or several (in particular the remaining) target pressure values ​​of the target pressure profile based on the initial and final pressure values. An exemplary calculation of the target pressure profiles is explained below in connection with Figures 4 and 5.

[0058] Preferably, the actuator elements 5 are each movable in a first direction of movement (e.g., vertically upwards) and a second direction of movement opposite to the first direction of movement (e.g., vertically downwards), and for each direction of movement, a respective final pressure value is recorded and a respective target pressure profile is generated. Preferably, a respective initial pressure value is also generated for each direction of movement. Advantageously, during the learning process, each pneumatic actuator 4 is pneumatically actuated, resulting in a movement in the first direction of movement, during which a respective initial pressure value and a respective initial pressure value are recorded, and a movement in the second direction of movement, during which a respective second initial pressure value and a respective second final pressure value are recorded.For each pneumatic actuator 4, a respective target pressure profile (associated with the first direction of movement) is calculated based on the first pressure start value and the first pressure end value, and a respective target pressure profile (associated with the second direction of movement) is calculated based on the second pressure start value and the second pressure end value. The target pressure profiles associated with the first direction of movement are used by the valve device 3 for movements of the actuator elements 5 in the first direction of movement, and the target pressure profiles associated with the second direction of movement are used by the valve device for movements of the actuator elements in the second direction of movement. For example, the first target pressure profiles are increasing, in particular monotonic, preferably strictly monotonically increasing. For example, the second target pressure profiles are decreasing, in particular monotonic, preferably strictly monotonically decreasing.

[0059] By providing individual target pressure profiles for each direction of movement, any existing hysteresis (especially due to friction and / or the springs 7) can be taken into account, preferably compensated.

[0060] The following section will explain in more detail how the target pressure profiles can be calculated.

[0061] Preferably, the valve device 3, in particular the control unit 11, generates a position-pressure mapping 23 for each pneumatic actuator based on the respective final pressure value (for example, the respective first final pressure value) and optionally the respective initial pressure value (for example, the respective first initial pressure value). By way of example, a position-pressure mapping 23 is generated, in particular calculated, for each pneumatic actuator 4 (and optionally for each direction of movement). Two position-pressure mappings 23 assigned to a respective pneumatic actuator 4 are also to be referred to together as a hysteresis curve. For example, exactly three or exactly six position-pressure mappings 23 are generated.

[0062] Figure 4 shows an example of a positional pressure

[0063] Figure 23 shows a characteristic curve in a pressure-position diagram. The position-pressure diagram 23 describes a relationship between the pressure p for actuating the respective pneumatic actuator and the position z of the respective actuator element 5. The position-pressure diagram 23, in particular the characteristic curve, can be linear or non-linear.

[0064] The position-pressure mappings 23 are expediently stored in a memory of the valve device 3, in particular the control 11, for example as characteristic curves, tables of values ​​and / or mathematical formulas.

[0065] The following explanations of the position-print figure 23 apply expediently to several or all position-print figures 23.

[0066] Position-pressure mapping 23 maps a plurality of position values ​​z to a plurality of pressure values ​​p, in particular such that each position value z is assigned a corresponding pressure value p. For example, position-pressure mapping 23 assigns the initial pressure value ps (for example, the first initial pressure value) to a first position value zel, which in particular describes the first end position. For example, position-pressure mapping 23 assigns the final pressure value pe (in particular, the first final pressure value) to a second position value ze2, which in particular describes the second end position. Pressure values ​​between the initial pressure value and the final pressure value are assigned to position values ​​between the first position value zel and the second position value ze2.These pressure values, which can also be referred to as intermediate pressure values, are expediently calculated by the valve device 3, in particular by the control unit 11, for example by means of an interpolation calculation or a curve fitting calculation, in particular on the basis of the initial pressure value ps, final pressure value pe, first position value zel and second position value ze2. For example, the position-pressure mapping 23 is calculated as a characteristic curve (in particular a straight line or a curve of another shape) that passes through the two pairs of values ​​(ps , zel) and (pe , ze2 ).

[0067] The points shown in Figure 4 are intended to represent pairs of values ​​consisting of a pressure value p and an associated position value z, which are stored, for example, as a table of values ​​and / or as a characteristic curve in the control unit 11.

[0068] As mentioned above, one (or two) respective position-pressure mappings 23 are calculated for each pneumatic actuator 4.

[0069] The valve device 3, in particular the control unit 11, is advantageously designed to convert a target position profile 24 into target pressure profiles 25 using the position-pressure curves 23. Figure 5 shows an exemplary target position profile 24 and three target pressure profiles 25: a first target pressure profile 25a, a second target pressure profile 25b, and a third target pressure profile 25c. The target pressure profiles 25 differ from one another. In Figure 5, the target pressure profiles 25 are depicted as differing significantly from one another; in reality, however, the differences between the target pressure profiles can also be smaller. The target position profile 24 is a time-dependent progression of a target position for the actuator elements 5. The target position profile 24 can also be described as a target position trajectory.The target position curve 24 comprises a plurality of position values ​​z, which are represented as points. The target position curve 24 is shown as an example of an upward slope, but can alternatively be downward slope or have a different shape. For example, the target position curve 24 has a curved shape and / or a decreasing slope over time (for example, to achieve a smooth transition to the target position zp). The last position value z of the target position curve 24 is the target position zp.

[0070] The target position profile 24 is provided by the valve device 3, in particular the control 11, and in particular calculated.

[0071] Based on the target position profile 24 and a first position-pressure figure 23 assigned to the first pneumatic actuator 4a, the valve device 3, in particular the control 11, calculates the first target pressure profile 25a, in particular by converting each of the position values ​​z of the target position profile 24 according to the position-pressure figure 23 into the respective assigned pressure value p.

[0072] Based on the target position profile 24 and a second position-pressure curve 23 assigned to the second pneumatic actuator 4b, the valve device 3, in particular the control unit 11, calculates the second target pressure profile 25b, in particular in an analogous manner to the first target pressure profile 25a. Based on the target position profile 24 and a third position-pressure curve 23 assigned to the third pneumatic actuator 4c, the valve device 3, in particular the control unit 11, calculates the third target pressure profile 25c, in particular in an analogous manner to the first target pressure profile 25a.

[0073] The calculated pressure values ​​p, which form the target pressure profiles 25, are represented as points.

[0074] According to the target pressure profiles 25, the pneumatic actuators 4 are then controlled by the valve device 3, in particular the pressure regulator units 9, especially simultaneously, in order to achieve the synchronous movement of the actuator elements 5.

[0075] Preferably, the target position profile 24 is provided position value by position value, and each provided position value is converted into three pressure values ​​after its provision, which are then used as target pressure values ​​for simultaneous pneumatic actuation of the pneumatic actuators 4. The pneumatic actuation can, in particular, take place before the complete target position profile 24 is provided and / or the complete target pressure profiles 25 are calculated.

[0076] Alternatively, it is also possible to first fully provide the target position profile 24 and / or fully calculate the target pressure profiles 25, and only then to begin the pneumatic actuation according to the target pressure profiles 25. With reference to the block diagram shown in Figure 2, an exemplary signal flow in the pneumatic system 1 will be discussed below.

[0077] The control unit 11 comprises a trajectory planner 26, which receives a target position signal 27 that defines the target position. Based on the target position signal 27, the trajectory planner 26 calculates the target position profile 24 and provides this to a position controller 28, which, using the position-pressure mapping 23, converts the target position profile 24 into the target pressure profile 25 and transmits this to the respective pressure regulator unit 9, in particular as an electrical signal.

[0078] The pressure regulator unit 9 compares a current target pressure value of the target pressure curve 25 with an actual pressure value 29 determined by means of the pressure sensor 14 and performs a venting or aeration of the pressure chamber 6 by means of the valve unit 12 in order to change the actual pressure value 29 towards the target pressure value.

[0079] The end position detection device 8 detects one or two end positions of the actuator element 5.

[0080] In particular, the end position detection device 8 detects when the respective actuator 5 reaches its respective end position. Preferably, the respective final pressure value is detected in response to the end position detection device 8 recognizing that the respective actuator 5 has reached its respective end position.

[0081] For example, the control unit 11 includes a monitoring unit 30, to which the current actual pressure value 29 is supplied and which is informed by the end position detection device 8 (for example by means of an end position signal 31) that the actuator element 5 is in an end position.

[0082] Preferably, the valve device 3, in particular the monitoring unit 30, is configured to determine diagnostic information concerning the pneumatic system 1, in particular the respective pneumatic actuator 4. The diagnostic information is determined, for example, based on a final pressure value and / or a target pressure profile and / or on a position-pressure mapping 23, which describes a relationship between the pressure for actuating the pneumatic actuator 4 and a position of the actuator element 5. For example, the monitoring unit 30 uses the current pressure value 29 and the end-position signal to monitor whether the final pressure value (and / or the initial pressure value) changes over time and provides the diagnostic information based on this monitoring. For example, the monitoring unit 30 provides an alarm 32 as diagnostic information, which is then sent to the position control 28.

[0083] For example, the monitoring unit 30 is designed to detect, during operation for the pneumatic actuators 4, a change in the relationship between the pressure and the position relative to the respective position-pressure figure 23 and, based on this detection, to provide the diagnostic information, in particular the alarm 32, and / or to make an adjustment to the position-pressure figure 23.

[0084] Control unit 11 also includes, for example, a

[0085] Training unit 33, which is trained, based on the

[0086] The position-pressure mapping 23 is determined from the current pressure value 29 and the end position signal 31 and provided to the position control 28. For example, the teaching unit 33 determines the final pressure value and / or initial pressure value based on the current pressure value 29 and the end position signal 31 and determines the position-pressure mapping 23 as explained above based on the final pressure value and / or initial pressure value.

[0087] The trajectory planner 26, the position control 28, the monitoring unit 30 and / or the teaching unit 33 are preferably designed as software components, which are expediently executed on a processor of the control 11.

[0088] Figure 2 shows only one pneumatic actuator 4; as explained above, preferably several, in particular three, pneumatic actuators 4 are provided. Preferably, each pneumatic actuator 4 has a respective position control 28, a respective monitoring unit 30 and / or a respective teach-in unit 33, which is / are designed in particular as explained above.

[0089] Figure 3 shows a block diagram of a variant of the pneumatic system 1 in which the end-position detection device 8 is not present (or not used). The differences between this variant and the variant discussed with reference to Figure 2 will be discussed below; apart from these differences, the present variant is expediently designed like the variant of Figure 2 discussed above. In the variant of Figure 3, the respective end-pressure value is detected in response to the valve device 3 recognizing, based on at least one control signal 34, that the respective actuator 5 has reached the respective end position. For example, each pressure regulator unit 9 provides its control signal 34 to the respective teach-in unit 33. The control signal 34 is, in particular, an electrical or digital signal.The control signal 34 is used to conveniently control the valve unit 12 in the pressure regulator unit 9 in order to adjust the size of a valve opening through which compressed air flows into (or out of) the pressure chamber 6.

[0090] Figure 6 shows the time profiles of a control signal 34, a pressure profile s 35, and the position z of an actuator 5, particularly during the learning run, for example, during a vertical upward movement of the actuator 5. The pressure profile 35 is, for example, a learning run target pressure profile with which the pressure regulator 9 is controlled during the learning run, particularly by the controller 11. Alternatively, the pressure profile 35 can also be the profile of the output pressure—that is, in particular, the actual pressure value 29—of the pressure regulator 9. For example, the pressure profile 35 has the form of an increasing straight line. The pressure regulator 9 sets its output pressure according to the learning run target pressure profile and generates the control signal 34 for this purpose.At a first time tl, when the actuator 5 begins to move, and at a second time t2, when the actuator 5 reaches an end position and does not move further, signal characteristics 36, 37, exemplified as signal jumps, occur in the control signal 34. These are expediently detected by the learning unit 33 in order to determine the initial pressure value ps and / or the final pressure value pe. The signal characteristics 36, 37 occur, for example, because the movement of the actuator 5 changes the volume of the pressure chamber 6, in particular increasing it. Therefore, the pressure regulator unit 9 must provide more compressed air t during the movement (and accordingly, via the control signal 34, provide a larger valve opening for the supplied compressed air t) in order to achieve the pressure profile 35.

[0091] At the first time point tl, the actuator 5 begins to move, and the time course of the control signal 34 exhibits the first signal characteristic 36 – for example, a jump upwards. In response to this first signal characteristic 36, the learning unit 33 detects the pressure value of the pressure curve s 35 present at the first time point tl as the initial pressure value ps.

[0092] At the second time point t2, the actuator 5 reaches its end position and does not move further. At the second time point t2, the time course of the control signal 34 exhibits the second signal characteristic 37 – for example, a downward jump. In response to this second signal characteristic 37, the learning unit 33 detects the actual pressure value 29 present at the second time point t2 (or the pressure value of the pressure curve s 35 specified at this time point tl) as the final pressure value pe.

[0093] Advantageously, the determination of a respective pressure start value ps and / or a respective pressure end value pe as explained above is carried out for each of the pneumatic actuators 4, in particular on the basis of the respective control signal 34 and the respective pressure profile s 35.

Claims

Claims 1. Method for synchronously moving at least two actuator elements (5) of a pneumatic system (1) for industrial automation, comprising at least two pneumatic actuators (4) and a valve device (3) for pneumatic actuation of the pneumatic actuators (4), wherein each pneumatic actuator (4) has a respective actuator element (5), comprising the steps: - pneumatic actuation of the pneumatic actuators (4) , so that each actuator element (5) is moved into a respective end position, - for each of the pneumatic actuators (4), detecting a respective pressure end value (pe) with which the respective pneumatic actuator (4) is actuated when the respective actuator element (5) reaches the end position, - based on the respective final pressure value (pe), generating a respective target pressure profile (25) for each pneumatic actuator (4), - pneumatic actuation of each pneumatic actuator (4) according to the respective target pressure profile (25) to move the actuator elements (5) synchronously to a target position (zp .

2. Method according to claim 1, wherein the actuator elements (5) are moved synchronously to each other over their entire path of movement towards the target position (zp).

3. Method according to claim 1, wherein during the movement of the actuator elements (5) to the target position (zp) no position control of the actuator elements (5) takes place and / or the pneumatic system (1) does not have position sensors to detect a position of the actuator elements (5) moving to the target position (zp).

4. Method according to one of the preceding claims, further comprising a wafer support (17) for placing a wafer (2) , and a positioning arrangement (19) movable relative to the wafer support (17) by means of the pneumatic actuators (4) , which serves to position the wafer (2) relative to the wafer support (17).

5. Method according to one of the preceding claims, wherein the positioning arrangement (19) comprises several contact points (21) for supporting the wafer (2), wherein each contact point (21) is assigned to a respective pneumatic actuator (4), and wherein the pneumatic actuators (4) are actuated according to the target pressure profiles (25) to move the contact points (21) synchronously in a direction of movement for positioning the wafer (2), such that the contact points (21) always have the same position relative to each other along the direction of movement during the positioning of the wafer (2).

6. A method according to any of the preceding claims, wherein a respective pressure start value (ps) is recorded for each of the pneumatic actuators (4), with which the respective pneumatic actuator (4) is actuated when the respective Actuator element (5) begins to move, whereby the respective target pressure profile (25) for each pneumatic actuator (4) is generated on the basis of the respective pressure end value (pe) and the respective pressure start value (ps).

7. Method according to one of the preceding claims, wherein, based on the respective final pressure value (pe) and / or one / the respective initial pressure value (ps), a respective position-pressure mapping (23) is generated for each pneumatic actuator (4), which describes a relationship between a pressure (p) for actuating the respective pneumatic actuator (4) and a position (z) of the respective actuator element (5), wherein, using the position-pressure mappings (23), a target position profile (24) is converted into the target pressure profiles (25).

8. Method according to one of the preceding claims, wherein diagnostic information concerning the pneumatic system (1) is determined on the basis of a final pressure value (pe) and / or a target pressure profile (25) and / or on the basis of a position-pressure mapping (23) which describes a relationship between a pressure for actuating the respective pneumatic actuator (4) and a position of the respective actuator element (5).

9. Method according to one of the preceding claims, wherein the actuator elements (5) are each movable in a first direction of movement and a second direction of movement opposite to the first direction of movement, and a respective final pressure value (pe) is detected for each direction of movement and a respective target pressure profile (25) is generated.

10. Method according to any one of the preceding claims, wherein the pneumatic system (1) has an end-position- Detection device (8), in particular limit switches, to detect when the respective actuator element (5) reaches the respective end position, and the respective pressure end value (pe) is detected in response to the detection by the end position detection device (8) that the respective actuator element (5) has reached the respective end position.

11. Method according to any one of claims 1 to 9, wherein the respective final pressure value (pe) is detected in response to the fact that, on the basis of at least one control signal (34) of the valve device (3), it is recognized that the respective actuator element (5) has reached the respective end position.

12. Pneumatic system (1) for industrial automation, comprising at least two pneumatic actuators (4) and a valve device (3) for pneumatically actuating the pneumatic actuators (4), wherein each pneumatic actuator (4) has a respective actuator element (5), wherein the pneumatic system (1) is configured to pneumatically actuate the pneumatic actuators (4) so ​​that each actuator element (5) is moved into a respective end position, to detect a respective end pressure value for each of the pneumatic actuators (4) with which the respective pneumatic actuator (4) is actuated when the respective actuator element (5) reaches the end position, to generate a respective target pressure profile for each pneumatic actuator (4) based on the respective end pressure value, and to actuate each pneumatic actuator (4) according to the respective target pressure profile in order to actuate the actuator elements (5). to move synchronously to a target position.

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